Text-book of botany, morphological and physiological . onia arise apparently without any definitearrangement in the interior of the upper side of the thallus. The formation of theantheridia commences by a circular group of cells of the outer layer separating fromthe subjacent tissue and thus producing a broad intercellular space, several of the low^erbounding cells of which, after some vertical divisions, rise up in the form of papillae,and form the antheridia, the position of which is represented in Fig. 216, B, an, theirmode of formation in Fig. 214. It is only w^hen the grains of chlorophyl
Text-book of botany, morphological and physiological . onia arise apparently without any definitearrangement in the interior of the upper side of the thallus. The formation of theantheridia commences by a circular group of cells of the outer layer separating fromthe subjacent tissue and thus producing a broad intercellular space, several of the low^erbounding cells of which, after some vertical divisions, rise up in the form of papillae,and form the antheridia, the position of which is represented in Fig. 216, B, an, theirmode of formation in Fig. 214. It is only w^hen the grains of chlorophyll in the wallsof the antheridia have assumed a yellow colour and the antherozoids are mature, thatthe roof of the cavity is ruptured, the antheridia opening at their apex and allowing theantherozoids to escape. The archegonia are formed in a manner still more different fromthat of all other Hepaticae (Fig. 218, C, ar). A row of cells perpendicular to the surface,resulting from the divisions of an upper segment of the apical cell of the shoot, becomes. /^> Fig. 217.—AtUhoceros l^FZis; s£ the young sporogoniuni; L the involucre (after Hofmeister, Xiso). filled with protoplasm ; the lowest cell of this row swells and becomes the central cell ofthe archegonium. While this cell is growing and rounding off, the other cells of therow become absorbed; the canal of the neck (Fig. 216, D, ar) which conducts to theinterior is thus formed, surrounded by six rows of cells. After fertilisation, theoosphere is first divided by an oblique wall; in the upper ceM, which becomes the apicalcell, other walls are formed inclining alternately right and left; but the walls after-wards arise in four alternating directions. While the immature sporogonium is thusbecoming transformed into a multicellular body enlarged below (Fig. 216,^), the sur-rounding tissue of the thallus divides repeatedly and grows into an involucre which isarched upwards and through which the elongating sporogonium afterwards
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectbotany, bookyear1875
